In a recent blog post, entrepreneur-author Ben Casnocha relayed this reality check: that as Mark Zuckerberg was sharing lessons from Facebook's rise to a room full of hard-hustling Silicon Valley folk, only two at the event were taking notes.

They were John Doerr and Ron Conway—guys synonymous with money and power in Silicon Valley.

So why would the two most successful people in the room, Zuck aside, be the ones taking notes? Casnocha has a theory: Experts take notes, while novices don't see the point.

To understand deeply, which is the foundation of effective thinking. In another blog post Casnocha contends that experts are constantly seeking to deepen the understanding of their core subject.

When we talk about core skills—the kind that you can build an adaptive career around—we mean that they are core because they lie at the foundation, at the center, at the antecedent of work that we do. Casnocha pulls from Edward B. Burger and Michael Starbird's 5 Elements of Effective Thinking, which we'll blockquote here:

Professional tennis players watch the ball; mathematicians understand a nuanced notion of number; successful students continue to improve their mastery of the concepts from previous chapters and courses as they move toward the more advanced material on the horizon; successful people regularly focus on the core purpose of their profession or life.

As we've discussed before, your mind can only handle so great of a cognitive load—people can only hold so many items in their working memory before they start to fall out. Active listening—that is, attending to the speaker and jotting down the things that catch your attention—lets us invest our working memory in paying attention to the new thing the Facebook founder just said rather than trying to remember that joke he made five minutes ago.

But it's not just about the initial notetaking: The idea is to create your own repository of knowledge. With luck, you'll continue to be awesome into your 80s—and if you're recording and organizing your knowledge from now until then, you'll have a mighty base of understanding.

This is a practice that badass learners systematize: Tim Ferriss, who is impeccable about his use of time, shows devotion to his notetaking, quipping that he takes notes "like some people take drugs" and that he trusts the weakest pen more than the strongest memory.

Casnocha has a lighter system, one that we ourselves wish we were already implementing:

I take lots of notes in paper mole skin notebooks; every week or so I go back with a different color pen and circle the key sentences; I then transfer these ideas to Evernote files on my computer; and finally, I blog/tweet/publish/email out the crispest, most important ideas or quotes.